1. Field of the Invention
The present invention relates to an isostatic press.
2. Description of the Related Art
The pressure is presently used for food processing, sterilization of foods, and the like in addition to for isostatic pressing applied to powders made of metal, ceramic, or the like, and there is carried out a process which synergistically applies heat along with the pressure in this case.
As a device which applies the pressure and the heat to a workpiece in this manner, Japanese Patent Laid-Open No. S61(1986)-124503 discloses a warm isostatic press which contains a workpiece inside a high pressure vessel, and introduces a heated pressure medium, thereby applying pressure and heat to the workpiece by means of the pressure medium.
However, in this warm isostatic press, a circulation passage of the pressure medium is not formed within the high pressure vessel. As a result, even if the heated and pressurized pressure medium is introduced into the high pressure vessel, depending on positions of an inlet opening and an outlet opening of the pressure medium formed on the high pressure vessel, the pressure medium which has flown in through the inlet opening may flow out from the outlet opening without circulating within the high pressure vessel, which prevents a desired heating effect from being attained. Moreover, there is no heat insulating material within the high pressure vessel, and there thus poses a problem that the pressure medium exchange heat with the high pressure vessel, resulting in a decrease of the temperature of the pressure medium.
To address the above problem, there is proposed a warm isostatic press which is equipped with a tubular bucket which can contain a workpiece in a high pressure vessel, thereby forming a circulation passage of a pressure medium within the high pressure vessel by means of the bucket (Japanese Patent Laid-Open No. S61(1986)-126998).
Though this warm isostatic press provides a better heating effect than the warm isostatic press disclosed in Japanese Patent Laid-Open No. S61(1986)-124503 for heating, there is no heat insulating member inside the high pressure vessel, the heat of the pressure medium is thus released to the outside of the high pressure vessel through the high pressure vessel, and there poses a problem that it is difficult to maintain the pressure medium within the high pressure vessel at a desired temperature. Moreover, since the pressure medium at a low temperature is in contact with the workpiece while circulating during the pressurizing, there is such a problem that the temperature accuracy decreases.
To solve the above problems, Japanese Published examined application No. H7(1995)-61238 discloses a high pressure processing device which, by forming a working zone for storing a workpiece using a heat insulating structure, and by providing the heat insulating structure within a high pressure vessel to restrain a releasing heat of a pressure medium which flowing into the working zone to the outside of the high pressure vessel. Moreover, in the high pressure processing device, when the pressure medium pressurized by a pump is pressure-fed to the high pressure vessel, the pressure medium is heated via a heating device provided outside to prevent the temperature from decreasing in the process of pressurizing, resulting in an increase in the temperature accuracy.
However, in the high pressure processing device according to Japanese Published examined application No. H7(1995)-61238, there is provided a configuration where the pressure medium is flown inside the heat insulating structure storing the workpiece, is flown upward inside the heat insulating structure, and is then flown out through a slit formed on a top end portion of the heat insulator into a space between the heat insulating structure and the high pressure vessel, the pressure medium, which is at a low temperature due to the heat exchange with the workpiece, thus comes into contact with the high pressure vessel which has a high heat capacity, and it is thus difficult to maintain high temperature state of the entire high pressure vessel by means of a heat exchange between the high pressure vessel and the pressure medium. As a result, in the high pressure processing device according to Japanese Published examined application No. H7(1995)-61238, it is not possible to efficiently provide a heat retention capability obtained by keeping the high pressure vessel at a high temperature, and there poses a problem that a proper temperature cannot be maintained for a long period in the working zone.